Because we are doing upgrade to over existing versions and SQL2000 cannot be subscriber to SQL7 Publisher/Distributor we must stop the inwards replication before topology 1 publisher is upgraded (because topology 1 publisher is also topology 2 subscriber creating the conflict).

Does someone have experience of risks involved in this operation (or of any articles on subject). We are worried of any potetnial data loss while inwards replication is swithed off. Also is there any risk involved when upgrading from SQL7 to 2000 while replication is running?

You must stop REPLICATION process until the upgrade process is finished, you must suspend transaction activity in the databases and suspend replication. Note that replication includes the creation and dropping of both routes and subscriptions